Field assemblies having pole pieces with dovetail features for attaching to a back iron piece(s) and methods of making same

Abstract

An electric motor, power tool using the electric motor, and method of making the electric motor includes making a stator that includes pole portions that have dovetail features that are received in corresponding recesses of the back iron portion.

1 . An electric motor, comprising: 
 a. a stator having a back iron portion and at least two pole portions on which field coils are disposed, each pole portion having a dovetail feature at a radial outer end of a neck that is received in a corresponding recess in the back iron portion; and    b. an armature disposed in the stator.    
   
   
       2 . The electric motor of  claim 1  wherein each pole portion has an axial length shorter than an axial length of the back iron portion.  
   
   
       3 . The electric motor of  claim 2  wherein each pole portion has opposed axial ends that gradually decrease in width.  
   
   
       4 . The electric motor of  claim 1  wherein each pole portion has opposed axial ends that decrease in width.  
   
   
       5 . A power tool, comprising: 
 a. a housing;    b. a motor disposed in the housing, the motor including: 
 i. a stator having a back iron portion and at least two pole portions on which field coils are disposed, each pole portion having a dovetail feature at a radial outer end of a neck that is received in a corresponding recess in the back iron portion; and  
 ii. an armature disposed in the stator.  
   
   
   
       6 . The power tool of  claim 5  wherein each pole portion has an axial length shorter than an axial length of the back iron portion.  
   
   
       7 . The power tool of  claim 6  wherein each pole portion has opposed axial ends that gradually decrease in width.  
   
   
       8 . The power tool of  claim 5  wherein each pole portion has opposed axial ends that gradually decrease in width.  
   
   
       9 . A method of making an electric motor, comprising: 
 a. separately forming a back iron portion, at least two pole portions, and a field coil for each pole portion wherein each pole portion is formed to have a dovetail feature at a radial outer end of a neck and the back iron portion is formed to have recesses for receiving the dovetail features of the pole portions;    b. disposing the field coils on the necks of the pole portions and then inserting the dovetail features of the pole portions into the corresponding recesses in the back iron portion; and    c. then securing the pole portions to the back iron portion.    
   
   
       10 . The method of  claim 9  including forming each pole portion to have an axial length shorter than an axial length of the back iron portion.  
   
   
       11 . The method of  claim 10  including forming each pole portion to have opposed axial ends that gradually decrease in width.  
   
   
       12 . The method of  claim 9  including forming each pole portion to have opposed axial ends that gradually decrease in width.